She is skinny. (negative) She is fat. (negative)
She is anorexic. (medical) She is tubby. (negative)
She is underweight. (negative) She is overweight. (negative)
She is thin. (negative) She is plump. (neutral)
She is slim. (positive) She is stocky. (neutral)
She is slender. (positive) She is bonny. (positive)